This appendix and the next one contain information regarding the
modules that can be found in the contrib
directory of the PostgreSQL
distribution. These include porting tools, analysis utilities, and
plug-in features that are not part of the core PostgreSQL system,
mainly because they address a limited audience or are too
experimental to be part of the main source tree. This does not
preclude their usefulness.

When building from the source distribution, these components are
not built automatically, unless you build the "world" target (see
step 2). You can build
and install all of them by running:

gmakegmake install

in the contrib directory of a
configured source tree; or to build and install just one selected
module, do the same in that module's subdirectory. Many of the
modules have regression tests, which can be executed by
running:

gmake check

before installation or

gmake installcheck

once you have a PostgreSQL
server running.

If you are using a pre-packaged version of PostgreSQL, these modules are typically made
available as a separate subpackage, such as postgresql-contrib.

Many modules supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have
installed the code you need to register the new SQL objects in the
database system. In PostgreSQL 9.1
and later, this is done by executing a CREATE EXTENSION command. In a fresh
database, you can simply do

CREATE EXTENSION module_name;

This command must be run by a database superuser. This registers
the new SQL objects in the current database only, so you need to
run this command in each database that you want the module's
facilities to be available in. Alternatively, run it in database
template1 so that the extension will be
copied into subsequently-created databases by default.

Many modules allow you to install their objects in a schema of
your choice. To do that, add SCHEMA schema_name to the CREATE EXTENSION command. By default, the objects
will be placed in your current creation target schema, which in
turn defaults to public.

If your database was brought forward by dump and reload from a
pre-9.1 version of PostgreSQL, and
you had been using the pre-9.1 version of the module in it, you
should instead do

CREATE EXTENSION module_name FROM unpackaged;

This will update the pre-9.1 objects of the module into a proper
extension object. Future updates to the
module will be managed by ALTER
EXTENSION. For more information about extension updates, see
Section 35.15.

Note, however, that some of these modules are not "extensions" in this sense, but are loaded into the
server in some other way, for instance by way of shared_preload_libraries.
See the documentation of each module for details.